public ulong GetUserId(string signedRequest)
        {
            var client = new global::Facebook.FacebookClient
            {
                AppId = Settings.AppId,
                AppSecret = Settings.AppSecret
            };

//            var result = client.Get("oauth/access_token", new
//            {
//                client_id = client.AppId,
//                client_secret = client.AppSecret,
//                grant_type = "client_credentials"
//            });
//            client.AccessToken = result.access_token;

            var userId = (client.ParseSignedRequest(signedRequest) as dynamic).user_id;
            
            return UInt64.Parse(userId);
        }